1Field of the Invention
The present invention relates to roofing systems, and, more particularly, to roofing systems that use lightweight insulating concrete with an overly base ply sheet and cap membrane on flat or low sloped roof areas.
2Discussion of the Related Art
Generally, roof systems that use lightweight concrete with or without insulation require a base sheet membrane to be mechanically installed to the lightweight concrete for the purpose of allowing moisture to migrate. Once the base sheet is mechanically attached to the lightweight concrete, additional layers of roofing membrane are attached to the base sheet by either self adhesive, heat weld or cold adhesive. This bonds the membranes together to make up the roof assembly. Despite the widespread use of the mechanically attached base sheet membrane, used in flat and low sloped roof systems, there are significant drawbacks associated with its use. In particular, the increased amount of penetrating fasteners that need to be installed in order to meet the wind uplift requirements actually damage the lightweight the concrete at corners and along the perimeter of the roof. The resultant damage to the lightweight concrete, caused by the closely spaced fasteners, eventually leads to deck failure. Furthermore, when the roof needs to be replaced, requiring removal of the base sheet and fasteners, holes are left in the lightweight concrete. Thereafter, a new base sheet membrane is installed, and new fasteners penetrate additional areas of the existing lightweight concrete deck. Consequently, further damage is caused to the lightweight concrete deck.
It should be noted that the benefit of using lightweight concrete in lieu of insulation is not only to provide a slope for the roof system, but also to provide the owner with an insulating system that will remain intact after re-roofing and continue to provide the owner the slope and insulating value for all future roof systems.
In view of these shortcomings of the traditional mechanically attached base sheet membrane, there exists an urgent need in the roofing industry for an alternative venting system for new and existing lightweight concrete deck structures which overcomes the above described problems. More specifically, there is a need for a venting system that will allow moisture to travel to the perimeter of the roof, where the moisture can exit the roof assembly. Further, there is a need for venting the top side of a new or existing lightweight concrete deck which will considerably reduce costs for labor and material by eliminating the installation of the base sheet membrane and fasteners that are currently required for attachment to the lightweight concrete deck.